Field of the Invention
The present invention relates to an imaging apparatus, and particularly relates to an imaging apparatus that performs a phase contrast detection type of focal point detection at the imaging face.
Description of the Related Art
With the related art, configurations performing a phase contrast detection type of focal point detection at an imaging face of an imaging apparatus are known. Japanese Patent Laid-Open No. 2010-288083, for example, discloses a CMOS imaging device that includes imaging pixels to generate image generation signals, and focal point detection pixels to generate phase contrast detection signals. Also, for frames in which focal point detection is performed, all imaging pixels of the imaging devices are exposed simultaneously, and the imaging signal generated as a result of this exposure is read out. For frames in which focal point detection is not performed, the imaging signals from the imaging devices are read out by a slit rolling read out. Further, FIG. 4 and paragraph 0018 of Japanese Patent Laid-Open No. 2010-288083 describe a collective electron shutter being performed to align accumulated point-in-time of all pixels.
However, despite that the configuration in Japanese Patent Laid-Open No. 2010-288083 does not perform the phase contrast detection type of focal point detection at the imaging face, but does perform the collective electronic shutter, enough consideration has not been given to the configuration of pixels to actually achieve these results. Referencing FIGS. 2 and 4 of Japanese Patent Laid-Open No. 2010-288083 illustrates that a charge generated at a photoelectric conversion unit is transferred together for all pixels to a floating diffusion (hereafter, FD). Also, this charge is accumulated in the FD until a timing for the read out of each row of pixels. The configuration of the FD is basically not suitable for long-term holding of charges. Specifically, it is difficult to create a configuration in which little dark current is generated during the signal holding period. Further, it is also difficult to remove noise signals related to the pixel signals. It is theoretically possible to remove noise by including several rows worth of circuits to hold noise signals in a column circuit, but the space taken by the column circuits may become large. Further, the length of the holding period for the noise signal column circuit differs for each row, which may decrease the precision of noise removal.